Motor vehicle headlight including a single light source for generating two different beams

ABSTRACT

A motor vehicle headlight of the type comprising a single light source, a reflector including two zones suitable for generating two different respective light beams, a closure glass, and masking means situated in the vicinity of the source and capable of being displaced for selectively masking the light rays delivered by the source and propagating towards at least one of the two zones. According to the invention the two zones of the reflector are disposed side by side, each of them extending over the entire height of the reflector, each zone of the reflector is constituted by a portion of a reflecting surface sufficing on its own to generate the associated beam, and the masking means comprise at least one screen which, in its masking position, is situated to one side of the source.

The present invention relates in general to motor vehicle headlights andmore particularly it relates to a headlight capable of emitting twodifferent types of light beam from a single light source by actingmechanically on the geometry of the co-operation between the source andthe reflector.

BACKGROUND OF THE INVENTION

More precisely, the invention relates to a motor vehicle headlight ofthe type comprising a single light source, a reflector including twozones suitable for generating two different respective light beams, aclosure glass, and masking means situated in the vicinity of the sourceand capable of being displaced for selectively masking the light raysdelivered by the source and propagating towards at least one of the twozones.

A headlight of this type is already known in the prior art.

More precisely, French patent number 1 296 036 describes (page 2,righthand column) a particular embodiment of a headlight in which thefilament is fixed relative to the reflector, and the reflector comprisesa parabolic top portion whose focus is offset behind the filament inorder to form a dipped beam, and a bottom portion which is alsoparabolic but which has its focus in the vicinity of the filament, so asto form a main beam in co-operation with the bottom portion. The twoportions of the reflector are separated from each other at a horizontalplane including the optical axis, while the masking screen is suitablefor selectively intercepting rays from the source propagating towardsthe bottom portion in order to change over between main beam and dippedbeam.

A major drawback of a headlight of this type lies in the fact that sincethe dipped beam cut-off is directly created by the edge of the, or each,masking screen, and since mechanical play is inevitable in the design ofsuch a moving masking screen, the position of the cut-off is notaccurately defined, and this is not compatible with the photometricrequirements laid down by various regulations.

This phenomenon is further accentuated in headlights of this type whichsatisfy current design trends, i.e. having a very small vertical extentwhile being very wide. This means that the cut-off is defined, at leastwith respect to the concentration images, by regions of the reflectorwhich are very far from the source and the screen, thereby giving riseto undesirable amplification of any error in the positioning of themasking screen.

Another drawback of known headlights lies in the difficulty in enhancingthe intensity of one beam to the detriment of the other. More precisely,given the above-mentioned requirement for small vertical extent, anyattempt at increasing the light in one of the beams requires thereflector to be made wider. Unfortunately, in this case, the other beamalso benefits from such an increase, such that the ratio between thequantities of light specific to each of the two beams remainssubstantially the same.

In addition, French patent Number 690 678 describes a headlightcomprising a parabolic mirror having a matt or dull side zone which ispermanently exposed to radiation from the source and having another zonewhich may be masked by a side masking element. This prior headlight isthus not capable of generating two different beams since it is only themaskable zone which is capable of forming a beam. This document is thusof no use in attempting to solve the problem to which the presentinvention relates.

The present invention seeks to mitigate the drawbacks of the prior artand to provide a headlight in which the photometric characteristics ofthe beam, and in particular the definition and the position of thecutoff of a dipped beam or of a foglight beam are independent of anypossible play or inaccuracy that may exist in the position of a maskingscreen used for forming the beam in question.

Another object of the present invention is to provide a headlight of thetype mentioned in the introduction and capable without difficulty ofbeing very small in vertical extent, as required by present-day designs.

Yet another object of the present invention is to provide a headlight inwhich it is easy to modify the area of the reflecting zone attributed toeach type of beam without having to modify the general configuration ofthe headlight.

Finally, the invention seeks to provide such a headlight in which thetwo beams formed can equally well be complementary or independent.

SUMMARY OF THE INVENTION

To this end, according to the present invention, the two zones of thereflector are disposed side by side, each of them extending over theentire height of the reflector, each zone of the reflector isconstituted by a portion of a reflecting surface sufficing on its own togenerate the associated beam, and the masking means comprise at leastone screen which, in its masking position, is situated to one side ofthe source.

Preferred aspects of the headlight of the invention include thefollowing:

at least one of the two zones of the reflector is constituted by asurface suitable, on its own, for generating a beam situated beneath acut-off which extends generally horizontally, and may be constituted bya surface suitable for forming images of the light source whose topmostpoints are situated in the vicinity of the cut-off, the cut-off may behorizontal or it may be a cut-off delimited by a horizontal half-planeand by a half-plane which slopes above the horizontal, in which case theother zone of the reflector is preferably constituted by surfacesuitable for generating a concentrated beam on the vicinity of theoptical axis;

the masking means comprise a single screen for selectively masking rayspropagating from the source towards said other zone, or alternativelythe masking means comprise two screens for selectively masking rayspropagating from the source towards respective ones of the two zones ofthe reflector, in which case, the screen suitable for masking the rayspropagating from the source towards the first zone of the reflector hasat least one small orifice passing therethrough in order to allow adetermined quantity of light to pass therethrough towards said firstzone;

advantageously, the, or each, masking screen comprises a plate pivotedabout a horizontal axis fixed to a direct light mask associated with thesource, said plate being suitable for being moved into a maskingposition by drive means associated with transmission means, e.g.comprising gears and a crank system; finally, the source is preferablyan arc lamp.

An essential advantage of a headlight of the invention lies in that thecut-off of the, or each, beam is not defined by the moving maskingscreen, but by the reflector itself. As a result the cut-off is definedwith excellent positioning and sharpness regardless of any play,vibration, etc. that may have an effect on the position or the stabilityof the screen.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention are described by way of example withreference to the accompanying drawings, in which:

FIG. 1 is a simplified front view of a headlight of the invention;

FIG. 2 is a horizontal section through the FIG. 1 headlight;

FIG. 3 is an axial vertical section through the headlights of FIGS. 1and 2;

FIGS. 4a and 4b are diagrammatic front views of the headlight of FIGS. 1to 3 showing two possible states thereof;

FIGS. 5a to 5d are diagrammatic front views showing four possible statesof a variant headlight of the invention; and

FIGS. 6a and 6b are side views through a specific embodiment of themasking device of the invention shown in two different positions.

DETAILED DESCRIPTION

With reference initially to FIGS. 1 to 3 and 4a & 4b, a headlight of theinvention comprises a lamp 100, a reflector 200, and a front closureglass 300. In this example the lamp is a discharge lamp suitable forproducing an elongate electric arc between two electrodes disposedsubstantially axially in the vicinity of the optical axis Ox in wellknown manner. 102 and 104 respectively designate the base and the sealedbulb of the lamp. Its electrical terminals are referenced 108. Becauseof the large amount of light flux emitted by a lamp of this type, adirect light mask 106 is additionally provided in order to avoiddazzling drivers or pedestrians situated in front of the vehicle. Inthis case, the mask 106 is in the form of a circular cylinder which isclosed at its front end and which has an open back end having a complexoutline such that rays directed towards optically inoperative portionsof the reflector (cheek pieces, . . . ) are intercepted by the mask.

Naturally, it would also be possible to use a filament lamp, e.g. a lamphaving a tungsten filament, or any other type of lamp including a singlelight source.

The reflector 200 is constituted, in this case, by a reflector which isboth low and wide, being truncated by substantially horizontal top andbottom cheeks 240 and 250. In accordance with an essential aspect of theinvention, the reflecting surface 200 is divided into two distinctreflecting zones 210 and 220 respectively suitable for emitting twodifferent types of light beam, and the separation between the two zonestakes place in the present example along the axial vertical plane xOz ofthe headlight. It would alternatively be possible for the separation torun along two half-planes intercepting on the optical axis Ox, butsloping significantly relative to the horizontal, as indicated by dashedlines P and P'. The areas of the respective reflecting zones 210 and 220can thus easily be altered, thereby altering the intensities of the twobeams.

For example, the lefthand zone 210 (as seen from in front) of thereflector may be constituted by a portion of a reflecting surfacesuitable on its own for generating a V-shaped cut-off specific tostandardized European dipped beams and without requiring assistance froma mask or the like. In practice, it may be constituted by one-half ofone of the surfaces described in French patents or patent applicationsnumbers 2 536 502, 2 599 121, and 2 609 148 in the name of theApplicant, and the respective contents thereof are hereby incorporatedin the present description by reference, and further details may beobtained by reference thereto.

In the present example, the righthand zone 220 of the reflectorconstitutes a portion of a surface suitable for generating a beam whichis essentially complementary to the dipped beam. It may be constituted,for example, by a portion of a paraboloid with the arc being off-centerrelative to the focus thereof, or else it may be constituted by one-halfof a surface as described in French patent application number 2 600 024,with the contents thereof being likewise incorporated herein byreference and which should be referred to for further details.

In addition, as shown diagrammatically in FIGS. 4a and 4b (but not shownin FIGS. 1 to 3 for reasons of clarity), the headlight includes amasking screen 420 which, in this case, is in the form of one half of acircular cylinder about a horizontal axis that coincides substantiallywith the optical axis, and which is hinged along one edge about an axis440 parallel to the optical axis and situated beneath the lamp, with thehinge axis being mounted, for example, on the direct light mask 106.

Drive means (not shown), e.g. an electric motor or an electromagnet,suitable for being controlled from the vehicle cabin, serve to displacethe screen 420 between a first or masking position (FIG. 4a) in which itcomes against the mask 106 in order to intercept radiation from the arcof the lamp directed towards the zone 220 of the reflector, and a secondor retracted position (FIG. 4b) in which it is moved away from the mask106, with the zone 220 now being exposed to radiation. It can beobserved that in this example the zone 210 is always exposed toradiation.

It is clear that in the situation shown in FIG. 4a, only the zone 210 isactive, and as a result the beam which is formed is a European dippedbeam. In this respect, it may be observed that the various surfacesmentioned above have the property of creating, on their own, the entirebeam even when only half of the surface is used. Given the very largequantity of light delivered by an arc source, the intensity of theresulting beam is more than adequate.

In the situation of FIG. 4b, the entire reflector participates increating the beam, and as a result the beam is constituted bysuperposing the dipped beam generated by the zone 210 and thecomplementary or additional beam generated by the zone 220, therebyconstituting a main beam.

Referring now to FIGS. 5a to 5d, four ways are illustrateddiagrammatically of using a headlight which has a first reflecting zone210 suitable for forming a dipped beam on its own, and a secondreflecting zone 220 in the form of a paraboloid focused in the vicinityof the arc of the lamp 100. Two masking screens 410 and 420, e.g. bothmounted and hinged about a common axis 440 situated beneath the lamp100, are associated with the zones 210 and 220 respectively for thepurpose of exposing each of them selectively to the light delivered bythe arc, or for masking them therefrom. This reflector is furthercharacterized in that the masking screen 410 corresponding to reflectorzone 210 includes one or more small orifices as indicated at 412 inorder to allow a determined quantity of the light delivered by the arcto pass to the reflector.

In FIG. 5a, both screens 410 and 420 are in the masking position, asshown, and only a small quantity of light from the arc can escape to thezone 210 which then reflects it normally in a forwards direction. Thisthus constitutes a "sidelight" function, projecting a small quantity oflight in front of the vehicle serving to mark the vehicle rather than toilluminate its path.

In FIG. 5b, the masking screen 410 is open. This situation is equivalentto that shown in FIG. 4a, and the headlight emits a dipped beam.

FIG. 5c shows the case where the masking screen 410 is closed while themasking screen 420 is open. Only the zone 220 of the reflectorparticipates in forming a beam, and as a result the beam is an ordinarymain beam concentrated on the optical axis.

Finally, FIG. 5d shows a last possibility offered by this reflector: byopening both screens 410 and 420 simultaneously, the main beam issuperposed on the dipped beam, thereby obtaining an extremely powerfulbeam providing visual comfort both at a distance and closer to thevehicle.

Thus, without requiring any electrical switching of the lamp, but byappropriately controlling the means for displacing the masking screens,this headlight is capable of providing four lighting functions, all ofwhich are of excellent quality.

FIGS. 6a and 6b show a practical implementation of the masking meansused in the context of the present invention. These figures show amasking screen 410 for selectively masking the lefthand portion 210 (asseen from in front) of the reflector from the radiation delivered by theelectric arc.

A common support (not shown) and fixed, for example, &:o the reflectoror to the headlight housing, and integrally molded therewith, has areversible electric motor 401 mounted thereon with its outlet shaft 401acarrying a first gear wheel 402. This wheel meshes with a stepdown geartrain constituted by gear wheels 403, 404, and 405. The final gear wheel405 has an eccentric crank-forming pin 406 to which the first end of aconnecting rod 407 is hinged.

The direct light mask 106 is essentially square in right cross-sectionin this case and it carries a pin 409 on a vertical lug 106a with themasking screen 410 being hinged thereto by a tab 410a. The free end ofthe tab 410a, i.e. its end opposite from the portion thereof acting as amask (relative to the pin 409), is provided with a pin 408 having theother end of the connecting rod 407 hinged thereto.

It will be understood that rotation of the motor 401 drives the gearwheels and thus the connecting rod so as to cause the screen 410 to passfrom its non-masking or retracted position as shown in FIG. 6a to itsmasking position as shown in FIG. 6b, and vice versa. In order to ensurethat the said screen is accurately positioned in each of its twopossible positions, end-of-stroke switches may be provided, for example,at appropriate positions on the transmission, or positioning may beservo-controlled, both of which solutions are well known to the personskilled in the art.

It may be observed that the masking screen 410 has an outline such that,when in the masking position, it masks all of the space situated betweenthe back edge of the mask 106 and the base 102 of the lamp, therebyeffectively preventing any radiation from reaching the reflecting zone210 of the reflector.

The present invention, by placing its reflecting zones side-by-side incombination with using reflecting surfaces which are suitable forforming cut-off beams without requiring a masking screen to participatein forming the cut-off, thus makes it possible firstly to providetwo-function headlights having a single source by making use of an arcsource known for its high luminosity but not used in the past inpractices because the time required to switch between two arcs isincompatible with regulations, and secondly to provide two-functionheadlights having a single source which are extremely small in verticalextent, thereby satisfying present design requirements well.

By using a single arc source, the present invention also makes itpossible to obtain substantial savings compared with headlight systemsthat include not only two expensive arc lamps, but also two equallyexpensive power supplies for the lamps.

Naturally, the present invention is not limited in any way to theembodiments described above and shown in the drawings. In particular,although it is particularly advantageous to use a discharge lamp forreasons of light yield, it is clear that the invention is stilladvantageous when used with conventional tungsten filament sources.

Further, any combination of beams other than that described above may beenvisaged. For example, one zone may be provided for forming astandardized European dipped beam as described above, while the otherzone may be a parabola which is optionally off-centered or which mayhave a surface suitable for forming a beam that is complementary to thedipped beam. In the above headlights, it is also possible to replace thezone that forms the dipped beam by a zone which suffices on its own toform a foglight beam, e.g. corresponding to the surface described inFrench patent application number 2 536,503 in the name of the presentApplicant, with the content thereof being hereby incorporated into thepresent description by reference.

Another possibility consists in the maskable zone 220 being constitutedby a portion of a paraboloid focused on the source and giving rise to anextremely concentrated "spot" beam, while the non-maskable zone 210 mayhave a surface such as that described in French patent applicationnumber 2 609 149 which, on its own, suffices for generating a broad mainbeam.

Finally, numerous variants are possible of the electromechanical maskingmeans as described above. For example, they may be driven by anelectromagnet instead of using an electric motor. It is also possible touse masking means which are not electromechanical, e.g. anelectro-optical screen suitable for taking up an opaque state and atransparent state, depending on the value of an electrical voltageapplied to its terminals.

In general, the person skilled in the art will know how to providemasking means capable of switching fast enough to satisfy regulations,in particular when switching from main beam to dip beam and back again,and when "flashing" headlights.

What is claimed:
 1. A motor vehicle headlight of the type comprising asingle light source, a reflector including two zones suitable forgenerating two different respective light beams, a closure glass,masking means situated in the vicinity of the source and capable ofbeing displaced for selectively masking the light rays delivered by thesource and propagating toward at least one of the two zones, said twozones disposed side-by-side, each zone extending over the entire heightof the reflector, each zone of the reflector comprising a portion of areflecting surface capable of generating associated beam, said maskingmeans comprising .[.at least one screen.]. .Iadd.two screens.Iaddend.,said .[.screen.]. .Iadd.screens.Iaddend.in .[.its.]. masking.[.position.]. .Iadd.positions.Iaddend.situated .[.to one.]. .Iadd.oneither.Iaddend. side of the source, at least one of the two zones of thereflector comprising a surface for generating a beam beneath a cut-offextending generally horizontally, the other zone of the reflectorcomprising a surface suitable for generating a concentrated beam in thevicinity of the optical axis, and said .[.screen.]..Iadd.screens.Iaddend. adapted to mask the rays propagating from thesource toward the .[.first zone.]. .Iadd.two zones.Iaddend. of thereflector and .Iadd.one screen.Iaddend. having at least one smallorifice therethrough in order to allow a determined quantity of light topass through said screen toward said first zone. .[.2. The combinationaccording to claim 1 wherein said at least one zone is defined by asurface adapted to form images of the light source whose top most pointsare situated in the vicinity of said cut-off..]. .[.3. The combinationaccording to claim 2 wherein the cut-off is delimited by a horizontalhalf-plane and by a half-plane sloping above the horizontal..]. .[.4.The combination according to claim 3 wherein said masking meanscomprises a single screen for selectively masking propagating from thesource toward said other zone..]. .[.5. The combination according toclaim 4 wherein said masking means further comprises a second screen forselectively masking rays propagating from the source toward anassociated zone of the reflector..]. .[.6. The combination according toclaim 5 wherein said at least one masking screen comprises a platepivoted about a horizontal axis fixed to a direct light mask associatedwith the source, and drive means and associated transmission means formoving said masking screen into a masking position..]. .[.7. Thecombination according to claim 6 wherein said drive means comprises anelectric motor, and wherein the transmission means comprises a gear andcrank system..]. .[.8. The combination according to claim 7 wherein thesource is an arc lamp..].
 9. A motor vehicle headlight of the typecomprising a single light source, a reflector including two zonessuitable for generating two respective light beams, a closure glass,masking means situated in the vicinity of the source and capable ofbeing displaced for selectively masking the light rays delivered by thesource and propagating toward at least one of the two zones, said twozones of the reflector disposed horizontally side-by-side, each zoneextending over the entire height of the reflector, each zone of thereflector comprising a portion of a reflecting surface defining on itsown an associated beam, at least one of the two zones defining a beamlimited by a cut-off, the position of the cut-off being independent fromthe position of the masking means, and said cut-off position definedonly by the relative positions of said zone and said source, saidmasking means comprising at least one screen which in its maskingposition is located to one side of the source opposite said zone.[.and.]. defining a beam limited by cut-off .[.from.]..Iadd.for.Iaddend. masking the other zone. .[.10. The combinationaccording to claim 9 wherein said at least one masking screen comprisesa single plate pivoted about a horizontal axis, which horizontal axis isperpendicular to the headlight axis, and means for moving said plateinto a masking position..]. .[.11. The combination according to claim 10wherein said plate moving means comprises drive means and associatedtransmission means..]. .Iadd.12. The combination according to claim 9wherein a least one zone is defined by a surface adapted to form imagesof the light source whose top most points are situated in the vicinityof said cut-off..Iaddend. .Iadd.13. The combination according to claim12 wherein the cut-off is a straight horizontal cut-off..Iaddend..Iadd.14. The combination according to claim 12 wherein thecut-.Iadd.off is delimited by a horizontal half-plane and by ahalf-plane sloping above the horizontal..Iaddend. .Iadd.15. Thecombination according to claim 9 wherein said masking means comprises asingle screen for selectively masking propagating from the source towardsaid other zone..Iaddend. .Iadd.16. The combination according to claim 9wherein said masking means further comprises a second screen forselectively masking rays propagating from the source toward anassociated zone of the reflector..Iaddend. .Iadd.17. The combinationaccording to claim 9 wherein said at least one masking screen comprisesa plate pivoted about a horizontal axis fixed to a direct light maskassociate with the source, and drive means and associated transmissionmeans for moving said masking screen into a masking position..Iaddend..Iadd.18. The combination according to claim 17 wherein said drive meanscomprises an electric motor, and wherein the transmission meanscomprises a gear and crank system..Iaddend. .Iadd.19. The combinationaccording to claim 9 wherein said source is an arc lamp..Iaddend.